1. Field of the Invention
The invention relates to novel bleach precursors, peracids generated therefrom and use of these materials in detergent compositions.
2. The Related Art
t active oxygen-releasing compounds
It is well known that active oxygen-releasing compounds are effective bleaching agents. These compounds are frequently incorporated into detergent compositions for stain and soil removal. Unlike the traditional sodium hypochlorite bleaches, oxygen-releasing compounds are less aggressive and thus more compatible with detergent compositions. They have, however, an important limitation; the activity of these compounds is extremely temperature dependent. Thus, oxygen-releasing bleaches are essentially only practical when the bleaching solution is heated above 60.degree. C. Extremely high amounts of the active oxygen-releasing compounds must therefore be added to the system to achieve any bleach effect. Although this would indicate the desirability of high temperature operation, high temperatures are both economically and practically disadvantageous.
Automatic household washing machines for cleaning laundry are normally operated at wash-water temperatures below 60.degree. C. Consequently, there has developed a need for substances which promote release of active oxygen at temperatures below 60.degree. C. These substances are generally referred to in the art as bleach precursors, although they have also been called promoters and activators. Normally, bleach precursors are used in conjunction with persalts capable of releasing hydrogen peroxide in aqueous solution, perborate being the most widely used persalt.
Typically, the precursor is a reactive compound such as a carboxylic acid ester that in alkaline detergent solution containing a source of hydrogen peroxide, e.g. a persalt, will generate the corresponding peroxy acid. The reaction involves nucleophilic substitution onto the precursor by hydroperoxy anions (HOO--) and is facilitated by precursors having good leaving groups. Often the reaction is referred to as a perhydrolysis.
One of the earliest patents in the area of precursor chemistry was U.S. Pat. No. 2,955,905 (Davies et al) which discloses esters as precursors such as phenyl acetate, phenyl benzoate, p-nitrobenzaldehyde diacetate and glycollic aldehyde triacetate among a wide variety of compounds.
Other patents of note are U.S. Pat. No. 4,283,301 (Diehl) which discloses a peroxygen bleach and a precursor of the general formula: ##STR1## wherein R is an alkyl chain containing from 5 to 13 carbon atoms, R.sup.2 is an alkyl chain containing from 4 to 24 carbon atoms and each Z is a leaving group as defined therein.
U.S. Pat. No. 4,751,015 (Humphreys et al) reports a series of quaternary ammonium substituted carbonate salts, one example of which has a choline moiety and a phenol sulphonate group at opposite ends of the carbonate function. Bis type compounds are also generically suggested at column 3, line 50.
U.S. Pat. No. 4,412,934 (Chung et al) reports compositions incorporating bleach precursors of the general formula: ##STR2## wherein R is an alkyl group containing from 5 to 18 carbon atoms and L is a leaving group.
Similar disclosures are found in U.S. Pat. No. 4,486,327 (Murphy et al), EP No. 0 098 129 (Hardy et al), EP No. 0 106 584 (Hartman), EP No. 0 106 634 (Chung et al), EP No. 0 120 591 (Hardy et al), EP No. 0 163 331 (Burns et al), EP No. 0 166 571 (Hardy et al), Ep No. 0 185 522 (Fong et al), EP No. 0 170 386 (Burns et al) EP No. 0 153 222 (Moyne et al), EP No. 0 153 223 (Moyne et al) and EP No. 0 202 698 (Nollet et al).
While the aforementioned precursors have all been reported effective at stain removal, there is still a need for more efficient systems. Stain removal efficiency may be improved either by a precursor that generates equivalent bleach at a lower precursor molar level or operates at lower levels of peroxide source. Not only do lower levels of peroxide source or precursor provide better economics, they also permit increased flexibility in detergent formulation.
Consequently, it is an object of the present invention to provide a detergent-bleach composition with a precursor that permits bleaching over a wide temperature range including that of under 60.degree. C.
It is another object of the present invention to provide certain novel bleach precursors which have hitherto not been described in the art.
Another object of the present invention is to provide a precursor that can be economically synthesized from readily available starting materials and in a minimum number of synthetic steps.
A still further object of the present invention is to provide novel peroxy acids generated from the bleach precursors by perhydrolysis with hydrogen peroxide or persalts.